Packet-based communications networks typically comprise several different address domains. For example, a particular company or enterprise may have its own network which is connected to another network such as the Internet. This is illustrated in FIG. 1, which is introduced for explanatory and informative purposes, which shows a network 10 of a first enterprise connected to a common network 11. Other enterprises may also have networks connected to the common network 11, such as enterprise 2 and its network 12 in FIG. 1. These different networks 10, 11, 12 typically each use a particular addressing scheme and number of addresses, one for each node within that network. Thus each network is an address domain.
The address domains may or may not overlap; that is, for two overlapping address domains, at least some of the addresses occur in both domains. In addition, an address domain may be either public or private with respect to other address domains. In the example shown in FIG. 1 an enterprise network 10 is private with respect to common network 11. That is, addresses of nodes within enterprise network 10 are not known to nodes within common network 11. However, common network 11 is public with respect to enterprise network 10. That is, addresses of nodes in common network 11 are known to nodes within enterprise network 10.
As is known in the art, address domains are connected via address translation nodes which act to associate or “translate” the address of an item in one domain into an address that is functional within another address domain. For example, one particular type of address translation node is a network address translator (NAT). Another example is a network address and port translator (NAPT). Both NATs and NAPTs are defined by the Internet Engineering Task Force (IETF) in RFC 3022.
Consider a situation in which a service provider wishes to provide voice over internet protocol or other similar services to enterprise 1. This is typically achieved using a control node (e.g. MGC1 in FIG. 1) which is part of the service provider's own network connected to the common network 11 via an address translation node 14. For example, consider an entity connected to enterprise network 1 via node MG1. This entity requires to set up a call, say a voice call, between itself and another entity connected to enterprise network 2 via node MG2. In order to achieve this a request is sent to the control node MGC1 which uses control signalling messages to set up a call path in each direction between the two entities. Once this has been set up, actual media packets can be sent between the two entities to carry out the call.
The nodes MG1 and MG2 are media gateways or any other suitable type of node which is able to allow user terminals or endpoints to access a packet-based network. For example, the media gateways each comprise a codec which is used to convert speech signals into digitised, packetised data suitable for transmission over the enterprise data network 1. In the example of FIG. 1 only one media gateway 1 is shown connected to enterprise network 1 for reasons of clarity. However, in practice, there is an increasing need for many media gateway nodes to be used. For example, each media gateway node may be located at a particular customer premises.
Several problems arise however when the number of media gateway nodes connected to enterprise network 1 increases. The present invention is concerned with both the recognition of those problems and providing means to address those problems.
The invention seeks to provide a method and apparatus for dealing with a plurality of access nodes in a private communications network which overcomes or at least mitigates one or more of the problems noted above.
Further benefits and advantages of the invention will become apparent from a consideration of the following detailed description given with reference to the accompanying drawings, which specify and show preferred embodiments of the invention.